local my_tab = {name="帅哥"}
local my_mt = {}
setmetatable(my_tab, my_mt)

-- set the __index metamethod:
my_mt.__index = function (tab, key)
   print("Hello, " .. key)
   return "cool world"
end

-- trigger the __index metamethod:
print("Goodbye, " .. my_tab["world"])
print("Goodbye, " .. my_tab["LavenLiu"])
print("Goodbye, " ..my_tab["name"])
